Ward Swingle, who died on 19 January 2015 at age 87, was the founding father of the Swingle Singers, the a cappella group that blended jazz rhythms with Baroque and classical music in a distinctive, easy-listening style. The group made its name with scat renditions of Bach: lots of “doob-a-do” and “bah-bah-badah” substituting for the keyboard strokes more commonly heard in works such as The Art of Fugue (BWV 1080).

Critics could be wary. “The history of pop music is littered with jazzed-up versions of the classics,” sniffed The Times after they packed the Albert Hall in April 1965, before conceding that some people “truly find that the music’s enjoyable qualities profit by being brought up to date”. Others believed that in the same way that Stanley Kubrick’s film 2001: A Space Odyssey introduced many people to Strauss’s Also sprach Zarathustra, so Bach with a swing was an enticing introduction to Johann Sebastian’s carefully knitted counterpoint.

Not only did Swingle and his minstrels receive endorsement at the box office, major classical names such as John Barbirolli, Yehudi Menuhin and Glenn Gould offered their backing. George Malcolm, the renowned harpsichordist, shared the stage with them at the Festival Hall in 1966 in a program entitled “Jazz Sébastien Bach,” which was also the name of their first album.

Meanwhile, contemporary composers came calling. Luciano Berio wrote his colorful and noisy four-movement Sinfonia for the Swingle Singers, which they premiered with the New York Philharmonic in 1968 and performed at the Proms in 1969, with the BBC Symphony Orchestra conducted by the composer.

Ward Lemar Swingle was born on September 21 1927 in Mobile, Alabama, where, he once said, the sounds of New Orleans float along the coast of the Gulf of Mexico. He took to the piano from an early age and with his older brother, Ira, played lunchtime concerts in the school cafeteria, garnering sufficient popularity to be elected as president and vice-president respectively of their student council. By the time he left school, Ward, Ira and one of their sisters, Nina, were touring with the Ted Fio Rito Orchestra.

He studied music at the Cincinnati Conservatory, where he met his future wife, a French-born violinist, and won a Fulbright scholarship to pursue his musical studies in postwar Paris, taking lessons there with the celebrated pianist Walter Gieseking. Soon he was working as a rehearsal pianist for Roland Petit’s Ballet de Paris at a time when Petit was exploring jazz rhythms in his choreography.

Swingle’s first singing work – his voice was a mellifluous tenor – was with Blossom Dearie’s Les Blue Stars, a French vocal group whose members included Christiane Legrand, the sister of Michel Legrand, the composer. From there he joined Mimi Perrin’s Les Double Six, which won acclaim for its electronic treatment of jazz standards.

As Perrin’s health deteriorated in the early 1960s, Swingle, Legrand and other members of the group began singing privately, experimenting with jazzed-up Bach arrangements with the aim of improving their collective vocal agility. By 1962 the eight-member group was performing in public as Les Swingle Singers. Their concerts proved to be great hits with audiences, especially in Britain, and their early recordings won five Grammy awards.

By the early 1970s Swingle felt that he had exhausted the repertoire possibilities with his Parisian singers. He also wanted to experiment with other techniques, including close-mic singing. Crossing the Channel in 1973 he set up Swingle II, or the New Swingle Singers. The traditional swing music remained, but listeners were now regaled with jazz renditions from a wider selection of musical traditions, ranging from Baroque to big band. As well as looking forward, the Swingle Singers now also began looking into music’s back catalogue, releasing a disc of madrigals with a jazz twist in 1974.

Britain proved to be fertile ground. There were invitations to music festivals around the country as well as plentiful radio work. In 1982, for example, the Swingle Singers appeared in a televised concert from St. Paul Cathedral performing the sacred music of Duke Ellington with Tony Bennett, Phyllis Hyman and McHenry Boatwright.

After recording the Berio Sinfonia under the baton of Pierre Boulez in 1984, Ward Swingle stepped back from frontline singing to return to the United States. He remained the group’s musical adviser, while also running vocal workshops and publishing his many musical arrangements. He was often invited to share the techniques that he had developed for the Swingle Singers with established groups, such as the Stockholm Chamber Choir and the BBC Northern Singers.

A decade later Swingle moved back to France, and latterly was living in Britain. His book Swingle Singing, published in 1999, tells not only the history of the group, but also takes a musicological look at the techniques that he developed.

Today the Swingle Singers, now a seven-member ensemble, continue to push the boundaries of vocal music while also making recordings for television programs and films, including Sex and the City. Around seventy alumni keep in touch regularly, many of them gathering to celebrate Ward Swingle’s eightieth birthday in 2007, when the Berio was heard once again at the Proms.

He is survived by his wife, Françoise Demorest, whom he married in 1952, and by their three daughters.